Recently, the performance of portable devices essential to modern living, such as an MP3 player and a mobile phone, has been remarkably improved due to development of audio and telecommunications technology.
For example, the MP3 player is a device that can be used for recording and reproducing MP3 files containing music or other audio data downloaded from the Internet or converted from other media. The MP3 player may include an earphone jack thereby enabling a user to listen to reproduced files through earphones.
In addition to reproducing MP3 data, the MP3 player may perform various other functions such as receiving FM radio for reproduction or recording, converting the output of an audio device into MP3 files, voice recording, dictionary applications, and games. The demand for more functions is continuously increasing.
In addition to its various functions, the MP3 player has numerous controllable parameters such as volume, MP3 file, beat parameters, equalizer parameters, and various menu parameters. A large display window is required to visually represent the various menus and settings and numerous switches are required enabling a user to control the functions and parameters.
As shown in FIG. 1, a conventional portable multimedia device 10 such as an MP3 player generally includes various switches 1 and 3 installed on its front and sides, and a display window 2 disposed on its front. Since the switches take up considerable space, it is difficult to increase the size of the display window 2 beyond a certain limit. In order to significantly increase the size of the display window 2, the entire device must be enlarged.
If the display window 2 is enlarged to span the entire surface of the device, the various switches 1 and 3 would then be installed on the sides thereby making operation inconvenient.
As an example of technology intended to solve this problem, a touch screen has been proposed. The touch screen is used in combination with a general soft display such as a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display panel (PDP), or an organic light emitting display (OLED), and is manufactured as a separate device mechanically engaged with a display screen.
FIG. 2 is a schematic side view of a conventional touch screen. The touch screen 20 includes a transparent substrate 12, which is generally formed of a rigid glass material but may alternatively be formed of a flexible material such as plastic. Various additional material layers for forming a contact detection device 14 of the touch screen 20 are formed on an upper surface of the substrate 12. The contact detection device 14 includes a converter and a circuitry required to detect physical contact in a manner that can be used to calculate a contact position. A cable 16 is connected to the circuitry so that various signals can be transmitted to and received from the touch screen 20. The cable 16 is connected to an external controller 18. The external controller 18 controls application of various signals of the touch screen 20 and calculates (x, y) coordinates where contact occurs on a contact part.
Conventional touch screen technology using the above basic structure may employ resistive, capacitive, ultrasonic, surface acoustic wave, or other contact detection techniques.
A resistive touch screen generates a voltage in proportion to a relative resistance of a circuit located at a contact point, and measures the voltage to calculate (x, y) coordinates of the contact point.
A capacitive touch screen uses current variations due to contact of a conductive material to calculate (x, y) coordinates of a contact point.
An ultrasonic method applies a theory in which a sound wave field is disturbed when an object contacts the touch screen and measures the disturbance to calculate (x, y) coordinates.
When the touch screen is adapted to a portable device such as a mobile phone or a remote controller, an input may be made by the press and touch of a stylus pen or by the touch of a user's fingertip. However, when the stylus pen is employed, more than a predetermined level of pressure should be applied, the touch screen is less durable, and it is troublesome for the user to carry the stylus pen in addition to the main body.
Examples of proposed solutions to the above problems are disclosed in Korean Patent Laid-open Publication No. 1999-75892 entitled “ELECTRONIC BOOK FOR DISPLAYING DATA DOWNLOADED FROM TELECOMMUNICATION NETWORK”, and Korean Patent Laid-open Publication No. 2004-103562 entitled “KEY-PAD COMBINED WITH TOUCH SCREEN”.
Korean Patent Laid-open Publication No. 1999-75892 discloses an electronic book for displaying content stored in a memory device, the electronic book includes: a liquid crystal display for displaying data stored in the electronic book; an input means such as a touch pen and a touch panel input device for inputting information and selecting from a menu displayed on a screen; a telecommunication network connection socket and a connection device for connecting to an external data telecommunication network; a computer connection socket and a computer telecommunication connection device for transmitting and receiving data stored in a computer; and keys for controlling various operations.
Korean Patent Laid-open Publication No. 2004-103562 discloses a key-pad combined with a touch input means integrally formed with or separately added to a display unit for displaying a key definition, the key-pad including: an upper layer having a predetermined number of keys to be pressed; and a lower layer having projections for transmitting pressure to the touch input means corresponding to each key of the upper layer, wherein the keys are disposed at key definition regions displayed on the display unit, the key definitions displayed on the display unit are formed in a visually recognizable manner, and the keys are spaced apart from the touch input means by a contactable gap.
However, as described above, the conventional art forces a user to use both hands to precisely input data when the user's fingertip contacts the screen. In particular, when a portable multimedia device employing a conventional touch screen is operated with one hand, it is easy to accidentally touch more than one key active region in an overlapping manner so that a precise contact value cannot be selected.
Also, it is troublesome for the user to have to look at the display window while operating the device to perform a desired function in a conventional portable multimedia device adopting the touch screen.